Doctors often encounter patients having problems with a particular muscle or nerve (e.g., pinched nerve in the back or neck). Typically, a doctor examines the health of the problematic muscle or nerve by performing an electromyogram (EMG) test. An EMG test generally includes two parts, a nerve conduction study and a needle examination.
The nerve conduction study generally relies on the premise that a nerve is something like an electrical wire. To see if the wire is functioning properly, one delivers an electrical current and evaluates the conductibility of the wire. Analogously, the nerve conduction study includes delivering an electrical current to a selected nerve or muscle and analyzing the nerve's conductibility. How well the selected nerve or muscle conducts the electrical current provides an indication of the health of the nerve or muscle. The physician generally performs the nerve conduction study by attaching a recording or sensing electrode to the surface of the skin of the patient and delivering the electrical current with a pair of electrodes. With delivery of the electrical current, the sensing electrode acquires response signals, referred to as compound motor action potential (CMAP) signals from the selected nerve or muscle. The amplitude of the acquired CMAP signal indicates how many nerve or muscle cells are firing together, and the velocity of the acquired CMAP signal gives an indication of the type of fibers firing. Even though amplitude information is an important parameter in evaluating the functional performance of a nerve or muscle, physicians generally rely only on the conduction velocity to evaluate the performance of the nerve. Physicians do not rely upon amplitude because it has a high level of variance and lesser degree of reproducibility.
Therefore, it is a primary object and feature of the present invention to provide an apparatus for enhancing evaluation of the functional performance of a selected nerve or muscle based on a nerve conduction study.
It is a further object and feature of the present invention to provide an apparatus for and method of studying the effect of pressure on a sensing electrode in regard to the amplitude level of a conduction signal acquired during a nerve conduction study.